1. Field of the Invention
The present invention generally relates to radiation lenses and, more particularly, to x-ray lenses comprising a plurality of sub-lenses drawn together which is useful in flaw detection and diagnostics in engineering and medicine.
2. Description of the Prior Art
The usage of different types of radiation (X-rays, gamma ray, neutral or charged particle radiation) in different fields, such as instrument making, medicine, microelectronics, etc., considerably broadened for the last 20-30 years. More powerful X-ray and safe neutron sources are made. These sources help to solve important fundamental and applied tasks of science and industry.
Unfortunately, x-ray sources are very expensive. To build such sources, as does the European Center for Synchrotron Radiation (Greno{grave over (b)}le, France), several states must cooperate. Therefore it is very important to create optical devices, which can significantly increase effective luminance of cheap and available sources.
In the late eightiesxe2x80x94early nineties of 20 century the lenses for controlling X-rays and other high-energy radiation were created.
The first lenses for radiation control (including divergent radiation focusing, parallel beam of divergent radiation, a parallel radiation focusing or other transformation) comprised a package of channels for radiation transportation, and in these channels the radiation experiences multiple total external reflections. Such lenses were made of mass of capillaries or polycapillaries, which pass through holes or cells of supporting systems, positioned on definite distances along the lens such as disclosed in U.S. Pat. No. 5,192,869. A lens is shaped like a barrel (i.e. it narrows down to both ends), if it is meant for a divergent radiation focusing; or a lens is shaped like a half-barrel (i.e. it narrows down to one end), if it is meant for transforming a divergent radiation to quasi-parallel radiation focusing. Later on the terms xe2x80x9cfull lensxe2x80x9d and xe2x80x9chalf lensxe2x80x9d, respectfully, became widespread to denote lenses of these two types.
Other forms of lenses are possible, different from xe2x80x9cclassicalxe2x80x9d barrel and half-barrel forms, for example, the lens is bottle shaped as the curved body with a geneatrix, having a knee, when the channels are parallel in one or two ends. Such lenses can be used as a radiation filter (for cutting the high-energy part of the source spectrum) for transforming a section size of an input beam, etc.
The lenses described above, relating to the lenses of the first generation, are handmade and very massive. Such lenses focus X-rays with a quantum energy up to 10 keV, and the focal spot is of order of 0.5 mm in diameter.
A monolithic lens is also known, in which the walls of neighboring channels contact each other along their full length and the channels themselves have variable along a length cross-section as disclosed for example in U.S. Pat. No. 5,570,408.
By means of these lenses it is possible to focus a radiation with a quantum energy up to 20-25 keV. A cross-section of a transportation channel is about 10 xcexcm, and sometimes it is possible to obtain the channels of up to 2-3 xcexcm size. The minimum size of a focal spot is of the same order. Nowadays these lenses, called lenses of the second generation, are the most effective X-ray concentrators, when using X-ray tubes as the sources. A weakness of monolithic lenses is that it is practically impossible to create lenses with sufficiently big diameter (2-3 cm and more) with submicron channels.
In international publications WO 96/01991 and WO 96/02058 a full lens and a half-lens are described, which are made as a package of micro-lenses, packed very close, each of these lenses is a monolithic lens. Such construction makes possible to obtain accordingly larger cross sizes than in a common monolithic lens. When an aperture increases, an acceptance angle of radiation of a point source increases as well. However, the cross section sizes of channels for radiation transportation and the sizes of the focal spot remain the same, as in a common monolithic lens, and the packing of micro-lenses for needed shaping of the lens must be hand-made.
The technical result, achievable with the suggested lens, implies that the degree of radiation focusing increases owing to decreasing of cross section of the channels, making possible to use the particles of higher energy, as well as simplifying the technology of producing owing to eliminating the necessity of individual adjustment of micro lenses, when packing them in a unified structure.
The suggested method has an analogue; it is the method according to U.S. Pat. No. 5,812,631. According to this method several (two or more) stages of drawing of stocks is realized (the stocks represent a package of stocks in a common envelope, obtained at the previous stage). The regime of drawing the product, which is starting material for producing a lens by cutting the section of this product, from the furnace makes possible in this method to produce a microlens at once. To produce a full lens the product must be drawn repeatedly from the furnace, and this product must be fed in the furnace by the other end. It complicates the technological process.
However, the other defect of this method is more important. It does not provide the pressure correlation, mentioned above, in capillaries and space between stocks. If this condition is not met thin-walled capillaries, which are usually used for producing lenses for the examined purpose, are compressed in the process of drawing (i.e. it is impossible to produce the lens suitable for use). Thus the method according to the U.S. Pat. No. 5,812,631 can be realized (i.e. it allows producing fundamentally efficient lenses) only with the use of capillaries, produced of thick-walled tubes (i.e. a channel diameter of such tube must be comparable with a wall thickness). The same proportion lasts in a ready lens; because of this it has low transparency. For example, if a diameter of a channel is approximately equal to a wall thickness, a transparency lowers by an order. It lowers additionally, because this known method provides producing only such lenses, in which inner envelopes are present, as this method does not include the operation of envelopes removing from the stock surface.
Analytical devices are among one of the applications of X-ray lenses. These devices are meant for structure analysis (density distribution) of objects (including medicine and other biological objects), and for analysis of elemental composition of products and materials. The use of radiation for these aims, namely X-rays, is known for a long time.
A quality new stage in progress of such devices began with the use of lenses for controlling radiation, used in such devices such as described in U.S. Pat. No. 5,497,008. This analytical device includes a radiation source, representing a neutral or charged particle radiation, and a means for positioning the object under study. This means is positioned so that it is possible to act on it by radiation of the source. Beside that the analytical device includes one or more radiation detectors (the detectors are positioned so that it is possible to act on them by radiation, passed through the object under study or excited in it), one or more lenses for transforming a radiation, representing a neutral or charged particle flux, and being positioned on the radiation path from the source to the object under study and/or on the path from the object under study to one or more said radiation detectors (the detectors include radiation transporting channels, adjoining by the walls, with total external reflection).
Thus known analytical device under U.S. Pat. No. 5,497,008 does not provide high energy, and also cannot create small focal spots, what limits an accuracy and resolution of the analysis.
A technical effect, achievable in the suggested analytical device, is the increase of precision and resolution of the analysis, and also the expansion of opportunities of the analysis at the expense of application of radiation with higher energies, that becomes possible due to advantages of an offered integral lens.
The devices for radiation therapy, including one or more radiation sources, representing neutral or charged particle flux (namely, X-rays, proton flux), an optical system for beam collimation of every source, and a device for positioning the patient""s body or its part to be irradiated, are known. When such a device, healthy tissues, being on a radiation path to a tumor, located deep, are irradiated intensively.
The suggested invention, relating to the device of radiation therapy, is aimed at obtaining the following technical result: a doze of irradiation, acting on the tissues around the tumor, decreases.
One more field of application of X-ray lenses is microelectronics, namely X-ray lithography.
The device is known for contact X-ray lithography, containing a source of soft X-rays, a lens for transforming a divergent radiation to quasi-parallel, including radiation transporting channels, adjoining by their walls, with total external reflection, and the means for placing a mask and substrate with the resist put on it ( see, U.S. Pat. No. 5,175,755).
In this patent the lenses of the first and second generation are suggested for usage in the lithography. However, any of these types of lenses does not provide the solving a problem of lithography in microelectronics. In assembled lenses (lenses of the first generation), in monolithic lenses (lenses of the second generation) the size of the channel on an input about 1 xcexcm and on an output about 0.1 xcexcm is technologically impossible to implement at the target aperture 10 cm2 and more, what is necessary for lithography in the microelectronics.
The technical result of the suggested invention, related to the device for contact lithography, is obtaining a means, suitable for use in the microelectronics.
It is also known from U.S. Pat. No. 5,175,755 a device for projection X-ray lithography. This device includes a source of soft X-rays, a lens for transforming a divergent radiation of the source to quasi-parallel, meant for the irradiation of the mask, a device for the mask positioning, a lens for X-ray image of the mask transmission with the decrease of its size to the resist, a means for placing the substrate with the resist put on it. In this case both said lenses include the radiation transporting channels, adjoining by their walls, with total external reflection.
This device, at use in it the lenses of the first and second generations (i.e. assembled and monolithic lenses), known at the moment, as well as the device for contact lithography, discussed above, are unsuitable for use in microelectronics in view of impossibility to gain in such lenses diameters of channels, providing required accuracy of presentation of the mask image on the resist.
The technical result of the invention, related to the device for the projection lithography, is the production of the device, suitable for use in the microelectronics.
The present invention is directed to a radiation lens made up of a plurality of sub-lenes. In particular, a bundle of capillaries capable of guiding x-rays or similar neutral or charged radiation are drawn (pulled) together in a gaseous atmosphere at a heat sufficient to soften and bond the capillaries to form a unified sub-lens. The pressure of the gas atmosphere outside of the capillaries is made less than the pressure inside the capillaries to prevent the capillaries from collapsing. Thereafter, a bundle of sub-lenses are similarly drawn together in the gaseous atmosphere and at a heat sufficient to soften and bond the sub-lenses together to form higher integration sub-lenses. This process is repeated, each time drawing together the previous integration level sub-lenses to form higher integration level lenses until a single unified lens is formed of the desired size. The ends of the capillaries are cut to form an input face of the lens and an output face of the lens. Capillaries at the input and/or output faces can be oriented toward a focal point for divergent radiation applications or oriented in parallel for quasi-parallel radiation applications.